Both of these game based animes are amazing and worth watching but the question is which one is better.
Sao started off awesome with Kirito getting stuck in the game world where if you die in the game you die in real life not to mention his relationship with Asuna it was truly an awesome first season and Sao 2 started off really well too but the second half was just disappointing and had no real point which was unfortunate for how much potential it had.

No game no life is also an awesome anime and has one similarity to Sao they both are In the game world..... That's all in No game no life there's a brother and sister Sora and Shiro as they were put into a world by the God Tet where all problems are settled with a simple game it is truly perfect and the only real problem I could find with it was that there were only twelve episodes.
Which one do you like better. And.... Go